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fold-const.c (fold_binary): Fold (X & 1) ^ 1 as (X & 1) == 0. 

* fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
	(X & 1) == 0.
	<BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.

	* gcc.dg/fold-even-1.c: New test case.

From-SVN: r111454
This commit is contained in:
Roger Sayle 2006-02-26 16:10:30 +00:00 committed by Roger Sayle
parent a861485caf
commit cef65eaa92
4 changed files with 72 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2006-02-26 Roger Sayle <roger@eyesopen.com>
* fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
(X & 1) == 0.
<BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.
2006-02-26 Roger Sayle <roger@eyesopen.com>
James A. Morrison <phython@gcc.gnu.org>

29
gcc/fold-const.c
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@ -8740,6 +8740,13 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
fold_convert (type, TREE_OPERAND (arg0, 0)),
fold_convert (type, TREE_OPERAND (arg1, 0)));
/* Fold (X & 1) ^ 1 as (X & 1) == 0. */
if (TREE_CODE (arg0) == BIT_AND_EXPR
&& integer_onep (TREE_OPERAND (arg0, 1))
&& integer_onep (arg1))
return fold_build2 (EQ_EXPR, type, arg0,
build_int_cst (TREE_TYPE (arg0), 0));
/* See if this can be simplified into a rotate first. If that
is unsuccessful continue in the association code. */
goto bit_rotate;
@ -8792,6 +8799,28 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
&& reorder_operands_p (arg0, TREE_OPERAND (arg1, 0)))
return omit_one_operand (type, arg0, TREE_OPERAND (arg1, 0));
/* Fold (X ^ 1) & 1 as (X & 1) == 0. */
if (TREE_CODE (arg0) == BIT_XOR_EXPR
&& integer_onep (TREE_OPERAND (arg0, 1))
&& integer_onep (arg1))
{
tem = TREE_OPERAND (arg0, 0);
return fold_build2 (EQ_EXPR, type,
fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
build_int_cst (TREE_TYPE (tem), 1)),
build_int_cst (TREE_TYPE (tem), 0));
}
/* Fold ~X & 1 as (X & 1) == 0. */
if (TREE_CODE (arg0) == BIT_NOT_EXPR
&& integer_onep (arg1))
{
tem = TREE_OPERAND (arg0, 0);
return fold_build2 (EQ_EXPR, type,
fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
build_int_cst (TREE_TYPE (tem), 1)),
build_int_cst (TREE_TYPE (tem), 0));
}
t1 = distribute_bit_expr (code, type, arg0, arg1);
if (t1 != NULL_TREE)
return t1;

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2006-02-26 Roger Sayle <roger@eyesopen.com>
* gcc.dg/fold-even-1.c: New test case.
2006-02-26 Roger Sayle <roger@eyesopen.com>
PR middle-end/21137

33
gcc/testsuite/gcc.dg/fold-even-1.c Normal file
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@ -0,0 +1,33 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-original" } */
int test1(int a)
{
return !(a & 1);
}
int test2(int b)
{
return (b & 1) == 0;
}
int test3(int c)
{
return (c & 1) ^ 1;
}
int test4(int d)
{
return (d ^ 1) & 1;
}
int test5(int e)
{
return ~e & 1;
}
/* { dg-final { scan-tree-dump-times "\\(a \& 1\\) == 0" 1 "original" } } */
/* { dg-final { scan-tree-dump-times "\\(b \& 1\\) == 0" 1 "original" } } */
/* { dg-final { scan-tree-dump-times "\\(c \& 1\\) == 0" 1 "original" } } */
/* { dg-final { scan-tree-dump-times "\\(d \& 1\\) == 0" 1 "original" } } */
/* { dg-final { scan-tree-dump-times "\\(e \& 1\\) == 0" 1 "original" } } */
/* { dg-final { cleanup-tree-dump "original" } } */